1. Field of the Invention
This invention relates to dopamine receptors from mammalian species and the genes corresponding to such receptors. In particular, it relates to the human dopamine receptor D5. Specifically, the invention relates to the isolation, cloning and sequencing of the human D5 receptor gene. The invention also relates to pseudogenes of the human D5 receptor gene, and to the isolation, cloning, sequencing and characterization of such pseudogenes. Specifically, the present invention also relates to two pseudogenes of the human D5 dopamine receptor, D5.psi.1 and D5.psi.2. The invention also relates to the construction of eukaryotic expression vectors capable of expressing the human D5 dopamine receptor in cultures of transformed eukaryotic cells and the synthesis of the human D5 dopamine receptor in such cultures. The invention relates to the use of such cultures of transformed eukaryotic cells producing the human D5 dopamine receptor for the biochemical and physiological characterization of the human D5 dopamine receptor and the development and testing of drugs useful for treating or preventing human disease.
2. Information Disclosure Statement
Dopamine is a neurotransmitter that participates in a variety of different functions mediated by the nervous system, including vision, movement, and behavior. See generally Cooper et al., The Biochemical Basis of Neuropharmacology, (Oxford University Press, NY 3d Ed. 1978), pp. 161-195. Dopamine is an important transmitter molecule at the synapses of neurons in the mesocortico-mesolimbic, nigrostriatal and tuberinfundibular pathways of the brain. To a lesser extent, dopamine is also thought to be involved in the signaling between some hippocampal neurons. The central dopaminergic tracts in the brain have been of considerable medical interest due to their association with several psychiatric and neurological disorders including psychosis, compulsive behavior, drug abuse and Parkinson's disease.
The diverse physiological actions of dopamine are in turn mediated by its interaction with specific receptors. The majority of dopamine receptors are concentrated in the mesocortico-mesolimbic, nigrostriatal and tuberinfundibular pathways. These neuronal circuits are known to influence mood, behavior, initiation of movement and prolactin secretion. The dopamine receptors are integral membrane proteins which interact with G proteins to transduce dopamine stimulation into intracellular responses. Dopamine is thought to evoke its physiological responses through the stimulation of at least two of the basic types of G protein-coupled receptors: D1 and D2, which respectively stimulate and inhibit the enzyme adenyl cyclase. Kebabian and Calne, 1979, Nature 277: 93-96. These receptors can be differentiated on the basis of their pharmacology, physiology and anatomical distribution. Alterations in the number or activity of these receptors may be a contributory factor in disease states such as Parkinson's disease (a movement disorder) and schizophrenia (a behavioral disorder).
A great deal of information has accumulated on the biochemistry of the D1 and D2 dopamine receptors, and methods have been developed to solubilize and purify these receptor proteins. See Senogles et al., 1986, Biochemistry 25: 749-753; Sengoles et al., 1988, J. Biol. Chem. 263: 18996-19002; Gingrich et al., 1988, Biochemistry 27: 3907-3912. The D1 dopamine receptor in several tissues appears to be a glycosylated membrane protein of about 72 kDa. Amlaiky et al., 1987, Mol. Pharmacol. 31: 129-134; Ninik et al., 1988, Biochemistry 27: 7594-7599. The D2 receptor has been suggested to have a higher molecular weight of about 90-150 kDa. Amlaiky and Caron, 1985, J. Biol. Chem. 260: 1983-1986; Amlaiky and Caron, 1986, J. Neurochem. 47: 196-204; Jarvie et al., 1988, Mol. Pharmacol. 344: 91-97. Much less is known about a recently discovered dopamine receptor, termed D3. Sokoloff et al., 1990 , Nature 347: 146-151. Dopamine receptors are also primary targets in the clinical treatment of psychomotor disorders such as Parkinson's disease and affective disorders such as schizophrenia. Seeman et al., 1987, Neuropsychopharm. 1: 5-15; Seeman, 1987, Synapse 1: 152-333. The three different dopamine receptors (D1, D2, D3) have been cloned as a result of nucleotide sequence homology which exists between these receptor genes. Bunzow et al., 1988, Nature 336: 783-787; Grandy et al., 1989, Proc. Natl. Acad. Sci. U.S.A. 86: 9762-9766; Dal Toso et al., 1989, EMBO J. 8: 4025-4034; Zhou et al., 1990, Nature 346: 76-80; Sunahara et al., 1990, Nature 346: 80-83; Sokoloff et al., 1990, Nature 347: 146-151, Van Tol et al., 1991, Nature 350: 610-614.
We have cloned and sequenced another human dopamine receptor which we termed D4. Zhou et al., 1990, Nature 347: 76-80. This receptor, the gene encoding it, and methods for using the receptor and its gene are disclosed in co-pending U.S. patent application Ser. No. 07/626,618, which is hereby incorporated by reference. The present invention relates to the isolation and characterization of yet another novel human dopamine receptor which we term D5. The dopamine D5 receptor gene has high homology to the human dopamine D1 receptor gene. The pharmacological profile of this receptor resembles that of the D1 receptor but with 2 distinct differences: the human D5 receptor shows a 5-fold lower affinity for the antagonist (+) butaclamol and a 10-fold higher affinity for dopamine. Further, the D5 receptor is able to stimulate adenylyl cyclase activity at dopamine concentrations which are 30-fold lower than required by the D1 receptor when expressed in the same cell line. These properties suggest that the D5 dopamine receptor disclosed as this invention may prove useful in discovering new types of drugs for a variety of psychological, neurological and motor-control diseases.